System and process for evaluating and validating additive manufacturing operations

ABSTRACT

A method of evaluating and validating additive manufacturing operations includes generating a multidimensional space defined by a plurality of bounds, each of the bounds being defined on a distinct parameter of an additive manufacturing process and each of the bounds being directly related to the occurrence of a vertical lack of fusion flaw, each of the parameters being a dimension in a multi-dimensional coordinate system, determining a coordinate position of at least one additive manufacturing operation within the multi-dimensional coordinate system, and categorizing the operation as free of vertical lack of fusion flaws when the coordinate position is within the multi-dimensional space.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Patent Application No.62/321328, which was filed on Apr. 12, 2016.

TECHNICAL FIELD

The present disclosure relates generally to additive manufacturing, andmore specifically to a process for evaluating and validating additivemanufacturing operation sequences.

BACKGROUND

Additive manufacturing is a process that is utilized to createcomponents by applying sequential material layers, with each layer beingapplied to the previous material layer. As a result of the iterative,trial and error, construction process, multiple different parametersaffect whether an end product created using the additive manufacturingprocess includes flaws, or is within acceptable tolerances of a givenpart. Typically, components created using an additive manufacturingprocess are designed iteratively, by adjusting one or more parameterseach iteration and examining the results to determine if the resultshave the required quality.

In some components, such as aircraft components, or other componentswith low tolerances, a substantial number of iterations can be requiredbefore determining a set of parameters that results in a component withan acceptable quality level. This iterative process can require monthsor years in order to refine a single part.

SUMMARY OF THE INVENTION

An exemplary method of evaluating and validating additive manufacturingoperations includes generating a multidimensional space defined by aplurality of bounds, each of the bounds being defined on a distinctparameter of an additive manufacturing process and each of the boundsbeing directly related to the occurrence of a vertical lack of fusionflaw, each of the parameters being a dimension in a multi-dimensionalcoordinate system, determining a coordinate position of at least oneadditive manufacturing operation within the multi-dimensional coordinatesystem, and categorizing the operation as free of vertical lack offusion flaws when the coordinate position is within themulti-dimensional space.

In another example of the above described exemplary method of evaluatingand validating additive manufacturing operations an operation that isfree of vertical lack of fusion flaws is an additive manufacturingoperation where vertical lack of fusion flaws in a resultant work pieceare below an acceptable threshold.

In another example of any of the above described exemplary methods ofevaluating and validating additive manufacturing operations theparameters include a beam power, a beam velocity, a spot size of a beam,a thickness of a powder bed, a boiling temperature of the powder bed,and a latent heat of an environment.

In another example of any of the above described exemplary methods ofevaluating and validating additive manufacturing operations each of theparameters is normalized to each other of the parameters.

In another example of any of the above described exemplary methods ofevaluating and validating additive manufacturing operations at least oneof the mathematical functions is a least partially empiricallydetermined.

In another example of any of the above described exemplary methods ofevaluating and validating additive manufacturing operations at least oneof the mathematical functions is determined via simulation.

Another example of any of the above described exemplary methods ofevaluating and validating additive manufacturing operations furtherincludes creating a work piece by causing an additive manufacturingmachine to perform the at least one additive manufacturing operation inresponse to categorizing the at least one additive manufacturingoperation as free of vertical lack of fusion flaws.

In another example of any of the above described exemplary methods ofevaluating and validating additive manufacturing operations at least oneof the parameters is partially unbounded.

In another example of any of the above described exemplary methods ofevaluating and validating additive manufacturing operations at least oneof the parameters is fully bounded.

In another example of any of the above described exemplary methods ofevaluating and validating additive manufacturing operations the at leastone additive manufacturing operation is a sequence of additivemanufacturing operations.

In another example of any of the above described exemplary methods ofevaluating and validating additive manufacturing operations the sequenceof additive manufacturing operations is an ordered list of alloperations required to create a part.

In another example of any of the above described exemplary methods ofevaluating and validating additive manufacturing operations generating amultidimensional space defined by a plurality of bounds comprisesgenerating multiple multidimensional spaces defined by a plurality ofbounds, each of the multiple multidimensional spaces corresponding toone or more flaws and at least one of the multidimensional spacescorresponding to the vertical lack of fusion flaw.

In one exemplary embodiment an additive manufacturing apparatus includesa chamber, a platform within the chamber, and a controller, thecontrolling including a processor and a memory, the memory storinginstructions for causing the processor to validate at least one inputoperation as generating a workpiece free of downskin roughness flaws bydetermining a multi-dimensional coordinate in response to receiving theat least one input operation, and comparing the multi-dimensionalcoordinate to a stored multi-dimensional space, the storedmulti-dimensional space being defined by a plurality of parametersincluding a beam power, a beam velocity, a spot size of a beam, athickness of a powder bed, a boiling temperature of the powder bed, anda latent heat of an environment.

In another example of the above described additive manufacturingapparatus the chamber further includes a powder bed fusion apparatus.

In another example of any of the above described additive manufacturingapparatus the powder bed fusion apparatus is a laser powder bed fusionapparatus.

In another example of any of the above described additive manufacturingapparatus the powder bed fusion apparatus is an electron beam powder bedfusion apparatus.

In another example of any of the above described additive manufacturingapparatus the memory further stores instructions for rejecting the atleast one input operation in response to the determinedmulti-dimensional coordinate falling outside the multi-dimensionalspace.

In another example of any of the above described additive manufacturingapparatus the multi-dimensional space is a space having four or moredimensions, and wherein each of the dimensions includes at least onebound corresponding to an operational parameter of an additivemanufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an exemplary additive manufacturingmachine.

FIG. 2 illustrates an example method for evaluating and validating oneor more additive manufacturing operations.

FIGS. 3 illustrates an example parameter that defines amulti-dimensional space.

FIG. 4 illustrates another example parameter that defines themulti-dimensional space.

FIG. 5 illustrates another example parameter that defines themulti-dimensional space.

FIG. 6 illustrates one exemplary flaw that can be accounted for usingthe process and system described herein.

DETAILED DESCRIPTION OF AN EMBODIMENT

FIG. 1 schematically illustrates an additive manufacturing machine 100,such as a laser powder bed fusion additive manufacturing machine. Inalternate examples, the powder bed fusion machine can be an electronbeam powder bed fusion machine. The exemplary additive manufacturingmachine 100 includes a manufacturing chamber 110 with a platform 120upon which a part 130 (alternatively referred to as a work piece) isadditively manufactured. A controller 140 is connected to the chamber110 and controls the additive manufacturing process according to anyknown additive manufacturing control system.

Included within the controller 140 is a processor 142 that receives andinterprets input operations to define a sequence of the additivemanufacturing. As utilized herein “operations” refers to instructionsspecifying operational conditions for one or more step in an additivemanufacturing process. The controller 140 can, in some examples, includeuser interface devices such as a keyboard and view screen. Inalternative examples, the controller 140 can include a wireless or wiredcommunication apparatus for communicating with a remote user inputdevice such as a PC.

Also included in the controller 140 is a memory 144. In some examples,the controller 140 receives a desired additive manufacturing operation,or sequence of operations, and evaluates the entered operation(s) todetermine if the resultant part 130 will be free of flaws. For thepurposes of the instant disclosure, free of flaws, or flaw free, refersto a part 130 or workpiece with no flaws causing the part or workpieceto fall outside of predefined tolerances. By way of example, thepredefined tolerances can include an amount of unmelt, a surfaceroughness, or any other measurable parameter of the part 130. Theprocessor 142 determines a set of parameters, based on the inputoperation(s) using a set of equations stored within the memory 144. Eachof the equations is configured to determine a specific output parameter,based on two or more variables of the input operation(s). By way ofexample, factors impacting the output parameters can include materialproperties, environmental conditions, or any other factors. Whiledescribed and illustrated herein as a component of a laser powder bedfusion additive manufacturing machine, the software configuration andoperations can, in some examples, be embodied as a distinct softwareprogram independent of the additive manufacturing machine, or includedwithin any other type of additive manufacturing machine.

The output parameters are combined to define a coordinate of theoperation(s) on a multi-dimensional coordinate system. Themulti-dimensional coordinate system is a coordinate system having morethan three dimensions. The processor 142 then compares the determinedcoordinate (the combined output parameter) against a multi-dimensionalspace defined in the multi-dimensional coordinate system, and stored inthe memory 144. The multi-dimensional space is formed from one or morebounds within each dimension. If the coordinate falls within themulti-dimensional space, the processor 142 determines that the inputoperation(s) is flaw free. If the coordinate falls outside of themulti-dimensional space, the processor 142 determines that the inputoperation(s) will result in a part 130 or workpiece that is flawed, andprevents the additive manufacturing machine 100 from creating the part130. In alternative examples, where the above described process isperformed in a computer independent of the additive manufacturingmachine 100, the computer provides an output informing the operator ifthe input operation(s) will result in a flawed part 130. If the inputoperation(s) will not result in a flawed workpiece, the operation(s) canthen be input in the additive manufacturing machine 100, and the part130 is created.

By using the defined multi-dimensional space, a technician can generatea part 130, or design a sequence of operations to generate a part 130,without requiring substantial empirical prototyping to be performed.This, in turn, allows the part to be designed faster, and with lessexpense, due to the substantially reduced number of physical iterationsperformed.

With continued reference to FIG. 1, FIG. 2 illustrates an example method200 for evaluating and validating a manufacturing sequence of additivemanufacturing operations. As described above, initially the technicianinputs a desired operation, or sequence of operations, into the computeror the additive manufacturing machine at an “Input Operation(s)” step210.

The computer/processor then calculates a number of parameters of theinput operation(s), and assigns a coordinate in a multi-dimensionalcoordinate system based on the calculated parameters in a “DetermineCoordinates of Operation(s)” step 220. In some examples, the number ofparameters, and thus the number of dimensions in the coordinate system,can be in excess of ten. In other examples, the number of parameters canexceed twenty. In an exemplary laser powder bed fusion additivemanufacturing process, each of the parameters is determined by amathematical function dependent on at least a power of a laser used anda scanning velocity of the laser. In alternative additive manufacturingsystems, the parameters can be dependent upon other variables, such as aheat source power and a translation speed.

The parameters can include, but are not limited to, beam focus, wire orpowder particle diameter, environmental conditions, particle density, orany number of other related parameters. Improper parameters can resultin output parts including excessive flaws. The possible flaws impactedby the parameters include, but are not limited to, balling, keyholing,keyhole pore formation, lack of fusion, and unmelt. Alternative additivemanufacturing systems can require, or use, alternative or additionalparameters to define the multi-dimensional space depending on thespecific features of the additive manufacturing system.

In an exemplary laser powder bed fusion process, balling refers to thecreation of spherical, or approximately spherical shapes within thestructure of the part due to the specific operations. The balling flawcorresponds to an expected amount of balling within the resultant part130. Similarly, keyholing refers to the creation of potentially unstablemelt pool shapes during the manufacturing process, and the keyholingflaw corresponds to an expected amount of keyholing in the resultantpart. Unmelt, refers to residual amounts of unmelted powder materialwithin the part.

While the specifically enumerated parameters are parameters of a laserpowder bed fusion additive manufacturing process, one of skill in theart having the benefit of this disclosure will understand that similarparameters related to any given additive manufacturing process could beutilized instead of, or in addition to, the enumerated parameters, andone of skill in the art, having the benefit of this disclosure, would becapable of ascertaining the relevant parameters for an alternativeadditive manufacturing system.

Once the coordinate of the sequence of operations is determined, thecomputer/processor compares the coordinate to the predefined space inthe multi-dimensional coordinate system in a “Compare Coordinates toSpace” step 230. As described above, the pre-defined space is amulti-dimensional space defining bounds along each dimension, with thedimensions corresponding to the parameters. If the determined coordinateof the sequence of operations is within the space, thecomputer/processor validates the sequence of operations as flaw free ina “Validate Operation(s) as flaw free” step 240. If, however, thecoordinate falls outside of the predefined space, the computer/processorrejects the sequence of operation as being flawed, or resulting in aflawed part, in a “Reject Operation as Producing Flaws” step 250.

The rejection of an input sequence as resulting in a flawed part cantake the form of the controller of an additive manufacturing system,such as a laser powder bed fusion additive manufacturing system,rejecting the sequence of operations. In alternative examples, where theprocess is performed on a computer, the rejection of the input sequenceof operations as resulting in a flawed part can take the form of awarning, or other prompt, informing the user that the proposed sequenceof operations is flawed.

By utilizing the predefined space, a technician can attempt severalsequences of operations for making a given part without being requiredto iterate multiple physical prototypes. One of skill in the art willrecognize, however, that the result of an operation may still includeunanticipated flaws, or be otherwise unsuitable even if the aboveprocess validates it. As such, in some examples, a minimal amount ofiteration is still required to develop an acceptable end part. In suchan example, each iteration of the sequence of operations is compared tothe space and subjected to the evaluation and validation process.Further, the equations defining the bounds of each dimension of themulti-dimensional space can be refined, in light of the new empiricaldata, between iterations to account for the newly determined flawedcoordinate. This refinement can be carried forward and applied tovalidation of further sequences of operations, or limited to the currentinput sequence of operations, depending on the nature of the parameterbeing refined. By way of example, if the parameter being refined isrelated to powder particle size, the parameter could be applied forward.However, if the parameter is related to the specific environmentalconditions, such as an ambient humidity, the parameter would not beuniversally applicable, and may be limited to the instant validation.

With continued reference to FIGS. 1 and 2 above, FIGS. 3-5 illustrateexample parameters that define dimensions and bounds of themulti-dimensional space discussed above. With regards to FIG. 3, apolynomial bound is defined and is dependent upon a beam power (P) and ascanning velocity (V) of a laser in a laser powder bed fusion additivemanufacturing system. The example of FIG. 3 defines a bound 330 relativeto a beam power (P) axis 310 and a scanning velocity axis (v). In theillustrated bound 330, everything on one side of the bound 330 defines a“flaw free” region 340, whereas everything on the other side of thebound 330 is known to produce unacceptable levels of flaws.

FIG. 4 illustrates a bound 430 that has a linear relationship between abeam power (P) axis 410 and a scanning velocity (V) axis 420. As withthe example of FIG. 3, everything on one side the bound 430 is a “flawfree” region 540, while everything on the other side of the bound 430 isknown to include unacceptable levels of flaws.

FIG. 5 illustrates a bound defined by two functions 530 and 550, witheverything between the two functions 530, 550 being a “flaw free” region540 and everything not between the two the functions 530, 550 beingknown to result in unacceptable levels of flaws.

Each of the plots of FIGS. 3-5 corresponds to one parameter, and onedimension of the multi-dimensional space. The specific equationsdefining the bounds within each parameter can be developed by one ofskill in the art, and are dependent on the specific part beingconstructed, and the corresponding tolerances of that part. The boundsand parameters are further dependent on the additive manufacturingprocess, the type of additive manufacturing machine being utilized andany number of other factors.

Each of the examples of FIGS. 3, 4 and 5 illustrates a partiallyunbounded parameter which defines a flaw free region 340, 440, 540. Inalternative examples, one or more of the parameters can include multiplebounds, and define an enclosed, finite, flaw free region.

To define the multi-dimensional space discussed above, each of theparameters of FIGS. 3, 4 and 5 are combined in a single coordinatesystem, with each parameter being a unique dimension. To facilitate thecombination, the parameters are normalized to a single scale. The flawfree regions 340, 440, 540 of each parameter defines a space within thatdimension that, when combined with the other parameters, forms amulti-dimensional space.

In some examples, the bounds of each parameter are determinedempirically, via iterative testing in a laboratory environment. In otherexamples, the bounds of each parameter are determined via mathematicalmodeling and simulations, and no iterations or physical tests arerequired. Even further still, in some embodiments, the bounds of theparameters are developed as a combination of both physical testing andtheoretical models with some parameters being based on empirical dataand some parameters being determined by theoretical modeling.

One of skill in the art, having the benefit of this disclosure willfurther understand that the multi-dimensional space can be utilized inthe reverse manner to determine appropriate parameters to create a givenwork piece. In such an example, the parameter coordinates for a givenoperation are entered into the computer/processer, and thecomputer/processor reverses the steps to determine an operation, orsequence of operations, that result in the desired parametercoordinates.

In one specific example, the system described above can account for, andprevent, operations that will result in a vertical lack of fusion. Avertical lack of fusion refers to a situation or component where avertical intersection of two adjacent scan tracks of an additivelymanufactured component does not form properly, and the adjacent scantracks within a single layer do not fuse together. By way of example, avertical lack of fusion can include pockets of powder between adjacentscan tracks, gaps, or any similar flaw between the scan tracks.

With continued reference to FIGS. 1-5, FIG. 6 illustrates two layers510, 520 of a workpiece 500 that includes a vertical lack of fusion flaw530 between multiple scan tracks 560 in one of the layers 510. Duringthe additive manufacturing process a beam scans a powder bed along thescan tracks 510 melting the powder in the appropriate locations. Whenthe beam is insufficiently sized or insufficiently powerful, the scantracks are too far apart, and the vertical lack of fusion flaws 530 arecreated.

The workpiece 500 includes a first horizontal layer 510 and a secondhorizontal layer 520. Due to certain specific parameters, such as beamspot size, scanning speed, melt pool shape, etc. during themanufacturing process, the scan tracks 560 within the first layer 510 donot intersect along the entire length of the track 560. In alternativeexamples, the vertical lack of fusion flaw 530 can extend across layers510, 520, and is not limited to a single layer 510.

By way of contrast, to the vertical lack of fusion 530, an optimal scantrack slightly overlaps the adjacent scan tracks resulting in a singlefully fused layer 510. The vertical lack of fusion can occur as a sideeffect of other flaws, such as a keyhole shaped melt pool, or as adistinct flaw independent of any other flaws.

As described above, flaws within a workpiece are the result of acombination of multiple parameters during the creation of the workpiece.The presence of vertical lack of fusion on scan tracks 560 in a singlelayer 510 is primarily impacted by the power of the beam, a velocity ofthe beam, a spot size of the beam, a thickness of the powder bed, aboiling temperature of the powder bed, the latent heat of theenvironment, and any similar parameters that would affect the sizeand/or shape of the melt pool.

The power of the beam refers to the magnitude of power provided to thebeam utilized to melt the particles forming the workpiece, and thevelocity of the beam refers to the velocity at which the beam is movedacross the powder bed in order to create the specific geometry of theworkpiece. The spot size of the beam, is the surface area of the powderbed covered by the beam. The thickness of the powder bed is the depth ofthe powder bed, relative to gravity. The boiling temperature of thepowder bed refers to the magnitude of heat required to melt the powderbed at the beam. The latent heat of the environment is the ambient heatwithin the additive manufacturing chamber.

Each of the key parameters outlined above is defined within a computerprogram using a function, or set of functions, as illustrated anddescribed above with regards to FIGS. 3-5. Once defined, the processdescribed above can be run on any proposed set of operations todetermine if the set of operations will include an unacceptable amountof vertical lack of fusion.

While a process and system for accounting for vertical lack of fusion isdescribed herein, one of skill in the art will understand that theprocess can be applied in conjunction with a system and process foraccounting for one or more additional flaws to further refine theoperations for running the additive manufacturing process. In someexamples, the combination of the vertical lack of fusion flaw andadditional flaw validation can be achieved by providing amultidimensional space for each flaw, and iterating the validationprocess for each space. In alternative examples, the bounds of eachparameter for each of the multiple flaws can be merged into a singlebound for the given parameter. A multidimensional space is thengenerated encompassing all of the parameters and the validation processcan be iterated once.

It is further understood that any of the above described concepts can beused alone or in combination with any or all of the other abovedescribed concepts. Further, one of skill in the art having the benefitof this disclosure will understand that additional enumerated, ornon-enumerated, parameters can impact the formation of any or all of theabove described flaws. As such, the above described system can beadapted to include additionally identified parameters, and still fallwithin the present disclosure. Although an embodiment of this inventionhas been disclosed, a worker of ordinary skill in this art wouldrecognize that certain modifications would come within the scope of thisinvention. For that reason, the following claims should be studied todetermine the true scope and content of this invention.

1. A method of evaluating and validating additive manufacturingoperations comprising: generating a multidimensional space defined by aplurality of bounds, each of said bounds being defined on a distinctparameter of an additive manufacturing process and each of said boundsbeing directly related to the occurrence of a vertical lack of fusionflaw, each of said parameters being a dimension in a multi-dimensionalcoordinate system; determining a coordinate position of at least oneadditive manufacturing operation within the multi-dimensional coordinatesystem; and categorizing the operation as free of vertical lack offusion flaws when the coordinate position is within themulti-dimensional space.
 2. The method of claim 1, wherein an operationthat is free of vertical lack of fusion flaws is an additivemanufacturing operation where vertical lack of fusion flaws in aresultant work piece are below an acceptable threshold.
 3. The method ofclaim 1, wherein the parameters include a beam power, a beam velocity, aspot size of a beam, a thickness of a powder bed, a boiling temperatureof the powder bed, and a latent heat of an environment.
 4. The method ofclaim 3, wherein each of said parameters is normalized to each other ofsaid parameters.
 5. The method of claim 3, wherein at least one of themathematical functions is a least partially empirically determined. 6.The method of claim 3, wherein at least one of the mathematicalfunctions is determined via simulation.
 7. The method of claim 1,further comprising creating a work piece by causing an additivemanufacturing machine to perform the at least one additive manufacturingoperation in response to categorizing the at least one additivemanufacturing operation as free of vertical lack of fusion flaws.
 8. Themethod of claim 1, wherein at least one of the parameters is partiallyunbounded.
 9. The method of claim 1, wherein at least one of theparameters is fully bounded.
 10. The method of claim 1, wherein the atleast one additive manufacturing operation is a sequence of additivemanufacturing operations.
 11. The method of claim 10, wherein thesequence of additive manufacturing operations is an ordered list of alloperations required to create a part.
 12. The method of claim 1, whereingenerating a multidimensional space defined by a plurality of boundscomprises generating multiple multidimensional spaces defined by aplurality of bounds, each of said multiple multidimensional spacescorresponding to one or more flaws and at least one of saidmultidimensional spaces corresponding to the vertical lack of fusionflaw.
 13. An additive manufacturing apparatus comprising: a chamber; aplatform within said chamber; and a controller, the controllingincluding a processor and a memory, the memory storing instructions forcausing the processor to validate at least one input operation asgenerating a workpiece free of downskin roughness flaws by determining amulti-dimensional coordinate in response to receiving the at least oneinput operation, and comparing the multi-dimensional coordinate to astored multi-dimensional space, the stored multi-dimensional space beingdefined by a plurality of parameters including a beam power, a beamvelocity, a spot size of a beam, a thickness of a powder bed, a boilingtemperature of the powder bed, and a latent heat of an environment. 14.The additive manufacturing apparatus of claim 13, wherein the chamberfurther includes a powder bed fusion apparatus.
 15. The additivemanufacturing apparatus of claim 14, wherein the powder bed fusionapparatus is a laser powder bed fusion apparatus.
 16. The additivemanufacturing apparatus of claim 14, wherein the powder bed fusionapparatus is an electron beam powder bed fusion apparatus.
 17. Theadditive manufacturing apparatus of claim 13, wherein the memory furtherstores instructions for rejecting the at least one input operation inresponse to the determined multi-dimensional coordinate falling outsidethe multi-dimensional space.
 18. The additive manufacturing apparatus ofclaim 13, wherein the multi-dimensional space is a space having four ormore dimensions, and wherein each of said dimensions includes at leastone bound corresponding to an operational parameter of an additivemanufacturing process.